President Trump expressed condolences Tuesday for the victims of the terrorist attack in Manchester, England, calling on all nations to unite in a battle to “obliterate this evil ideology.”

“We must drive out the terrorists and the extremists from our midsts, obliterate this evil ideology and protect and defend our citizens and people of the world,” Mr. Trump said at the Israel Museum in Jerusalem. “All civilized nations must be united in this effort.

He said the horrific attack on a crowd of mostly children at an Ariana Grande concert, which killed 22 people and injured dozens more, underscored the urgent mission of his first trip abroad: Uniting Muslims, Jews and Christians to confront radical Islamic terrorism.

“This trip is focused on that goal, bringing nations together around the goal of defeating the terrorism that threatens the world and crushing the hateful ideology that drives it so hard and seems to be driving it so fast,” he said.

Mr. Trump also reaffirmed the U.S. alliance with Israel, a relationship strained during the Obama administration.

“I make this promise to you. My administration will always stand with Israel,” Mr. Trump said.

The president has used his first trip aboard to prod countries across the Middle East and Europe to step up the fight against Islamic terrorism.

He began the journey in Saudi Arabia, telling a gathering of 50 leaders form Muslim countries that they must root out extremism within their countries.

Mr. Trump then spent two days in Israel, including meeting earlier Tuesday with Palestinian President Mahmoud Abbas.

Later, Mr. Trump will travel to Rome for an audience with Pope Francis at the Vatican.

At the museum, Israeli Prime Minister Benjamin Netanyahu thanked Mr. Trump for his “steadfast friendships to the Jewish people and the Jewish state.”